1. Field of the Invention
This invention relates to power transmission belts and, more particularly, to a method of treating a power transmission belt/belt sleeve to produce a vulcanized power transmission belt. The invention is also directed to a treating system in which the inventive method can be performed.
2. Background Art
In an exemplary belt forming process, an unvulcanized belt sleeve is formed with laminated compression rubber, tension rubber and adhesive rubber layers, with load carrying cords being embedded in the adhesive rubber layer between the compression and tension rubber layers. Typically, these components are formed around a mold. An elastically deformable cylindrical jacket is concentrically located around the belt sleeve. The mold with the belt sleeve and jacket thereon is then placed on a supporting stand in a vulcanizing vessel. An elastic packing material is disposed between the belt sleeve and the mold. The supporting stand is directed through an open upper portion of the vulcanizing vessel and is supported at the bottom of a chamber defined by the vessel. The open upper end of the vessel is then sealed with a cover. The belt sleeve is then vulcanized by applying high pressure vapor against the jacket, with low pressure vapor being directed into the mold.
After vulcanization, the jacket is removed and a grinding wheel, with a plurality of V-shaped ribs and a cutting surface thereon, is used to grind the belt sleeve to form a plurality of V-shaped ribs on a surface thereof. An exemplary grinding system is shown in Japanese Patent Publication No. 7-37084.
In this conventional method, the high pressure vapor applied to the jacket forces the jacket against the radially outwardly facing surface of the belt sleeve to thereby expel air from the space between the jacket and the mold. The unvulcanized belt sleeve is thereby vulcanized and solidified to maintain a predetermined shape. Ideally, the vulcanized belt sleeve assumes a rigid, predetermined shape without there being any captured air bubbles in the belt sleeve.
This type of jacket is conventionally pre-formed by wrapping an unvulcanized rubber layer, with a predetermined thickness, around a mold to define a jacket body. A radially outwardly extending flange is then formed at one axial end of the jacket body. A separate cylindrical jacket is fitted over the jacket body and abuts to the flange. This subassembly is then placed in a vulcanizing vessel and the primary jacket is vulcanized and thereafter released from the mold.
While the conventional method of vulcanizing using custom formed jackets, as described above, has been effective, there are a number of problems associated with this process. First of all, the jackets are custom designed for a specific belt sleeve configuration. Thus, in belt manufacturing operations where multiple belt sleeve configurations are formed, an equal number of jackets must be kept on hand and readily accessible for use. In some manufacturing facilities, these multiple jackets may take up a significant amount of valuable space.
Additionally, in some operations, jackets of a particular size may be used infrequently. Each time such little used jackets are needed, visual inspection of the jackets may be required.
In high volume belt production facilities, efficiency is important. In the same facilities, belt sleeves of different size may be produced somewhat randomly. To efficiently operate, it is important that an appropriately sized jackets be readily accessible to be picked up and placed on the belt sleeve at the pre-vulcanization station. However, generally, no matter how the stored jackets are organized, inevitably the selection and attachment of the jackets takes a considerable amount of time, which may limit production on a particular line, which may in turn result in lost time in changing lines.
In order to produce high quality belts, it is important to prevent vapor leakage through the jackets as a result of which penetration of the vapor into the unvulcanized belt sleeves may occur. Special steps must be taken to avoid this situation. Jackets that have been used for a long period of time must be carefully and regularly checked to determine that the supporting flanges and surfaces contacting the belt sleeve have not deteriorated. The flange region must also be inspected to make certain that no dust or foreign material has adhered to or accumulated at the flanges. Further, the jacket length and circumference may change over time, and it is thus important that these dimensions be regularly checked. A poor quality jacket may result in bubble formation within the unvulcanized belt sleeve, which detracts from the integrity and appearance of the belts that are formed from the sleeve.
As new jackets are being substituted for used and deteriorated jackets, the new jackets must be pre-heated in the vulcanizing vessel prior to being used on an unvulcanized belt sleeve so that the jackets are expanded to the desired length and circumference for the associated belt sleeves with which they are used. Thus, the break in for new jackets introduces another potential time loss on production lines.
The invention contemplates a method of treating a power transmission belt/belt sleeve of the type having an endless body with a length extending around an axis and a radially inwardly facing surface and a radially outwardly facing surface. The method includes the steps of wrapping at least one sheet of vapor-impervious film against and around the radially outwardly facing surface of the belt/belt sleeve body and vulcanizing the belt/belt sleeve with the at least one sheet of vapor-impervious film wrapped around the belt/belt sleeve body.
In one form, the belt/belt sleeve body has axially spaced, axially facing ends and the sheet of vapor-impervious film is wrapped over at least part of each of the axially spaced, axially facing ends of the belt/belt sleeve body.
The method may further include the step of mounting the belt/belt sleeve on a mold, with the vulcanization taking place with the belt/belt sleeve mounted on the mold.
After vulcanizing the belt/belt sleeve, the at least one sheet of vapor-impervious film may be removed from the belt/belt sleeve body.
The radially outwardly facing surface of the belt/belt sleeve body may be treated after removing the at least one sheet of vapor-impervious film.
The treating of the belt/belt sleeve may involve grinding the radially outwardly facing surface of the belt/belt sleeve body.
The grinding may involve forming at least two groves in the belt/belt sleeve body through the radially outwardly facing surface to define at least one V-shaped rib extending along the length of the belt/belt sleeve body.
Alternating grooves and teeth may be formed along the length of the belt/belt sleeve body.
The grooves and teeth may be formed at the radially inwardly facing surface of the belt/belt sleeve. With the grooves and teeth so formed, the at least one sheet of vapor-impervious film may be removed after vulcanizing after which the radially outwardly facing surface of the belt/belt sleeve is ground.
The at least one sheet of vapor-impervious film may be spirally wrapped or wrapped in a single turnaround the belt/belt sleeve body.
In one form, the belt/belt sleeve body has axially spaced, axially facing ends which join to the radially outwardly facing surface of the belt/belt sleeve body at first and second corners. A sealing material, in addition to the vapor-impervious film, may be applied at at least one of the first and second corners prior to vulcanizing the belt/belt sleeve.
The sealing material may be at least one of rubber-impregnated canvas or non-woven fabric.
The invention also contemplates a treating system including a belt/belt sleeve having an endless body with a length extending around an axis and a radially inwardly facing surface and a radially outwardly facing surface, at least one sheet of vapor-impervious film against and extending around the radially outwardly facing surface of the belt/belt sleeve body, and a vulcanizing vessel in which the belt/belt sleeve, with the at least one sheet of vapor-impervious film thereon, resides and in which a vulcanization process can be carried out.
In one form, the belt/belt sleeve body has axially spaced, axially facing ends and the at least one sheet of vapor-impervious film extends at least partially over the axially spaced, axially facing ends of the belt/belt sleeve body.
The belt/belt sleeve body may be mounted on a mold.
The vapor-impervious film may be a synthetic resin.
In one form, the belt/belt sleeve body has axially spaced, axially facing ends which join to the radially outwardly facing surface of the belt/belt sleeve body at first and second corners and the treating system further has a sealing material which is applied over the vapor-impervious film at at least one of the first and second corners.
The sealing material may bridge between the belt/belt sleeve and a mold on which the belt/belt sleeve is mounted at the at least one corner.
The sealing material may be at least one of rubber-impregnated canvas and a non-woven fabric.
The at least one sheet of vapor-impervious film may be spirally wrapped or wrapped in one turn around the outwardly facing surface of the belt/belt sleeve body.
The radially inwardly facing surface of the belt/belt sleeve body may have alternating grooves and teeth along the length of the belt/belt sleeve body.